Thermostat



May 22, 1934. T. o. HALL 1,959,954

THERMOSTAT Filed ,Afiril l, 1932 2 Sheets-Sheet 1 /7 /4. /8 22 INVENTOR W1000fi 0. flea.

May 22, 10934. Q HALL 1,959,954

THERMOS'IAT Filed April 1, 1932 2 Sheets-Sheet 2 INVENT 0 75500005 him BY J L A'FTORNEY. 1

Patented May 22, 1934 THERMOSTAT Theodore 0. Hall, New York, N. Y., assignor to Hall & Connolly, Inc., New York, N. Y., a corporation of New York Application April 1, 1932, Serial No. 602,411

12 Claims.

This invention relates to thermostats for controlling electrical circuits. It has especial adaptation to thermostats for controlling the feed of the electrodes of arc lamps used in projector or searchlight work. According to my invention I prefer to enclose the contacts in a vacuum tube so that oxidation of' the contact points is prevented. The thermostatic element or elements on the other hand are preferably located in the open air so as to be engaged by a beam from from the arc. The thermostat is also preferably compensated for temperature changes of the surrounding air. To this end a pair of opposed thermostatic strips are employed, connected by flexible strips at each end and adjustably flexed at their centers. The thermostat contacts are arranged to be actuated by the differential pull of the two thermostat strips on a connecting strip..

Obviously my invention is susceptible of various modifications within the scope of the appended claims.

Referring to the drawings showing several preferred forms of my invention,

Fig. 1 is a side elevation of my improved thermostat.

Fig. 2 is a front elevation of the same.

Fig. 3 is a top view, partly in section, of the same.

Fig. 4 is a sectional view of the vacuum contact means I prefer to use on my thermostat.

Fig. 5 is a plan view, partly in section, of a projector lamp mechanism showing the position of the thermostat on thesame.

As shown, my thermostat comprises two thermostatic elements 1 and 2 each comprising the usual bimetallic strips and connected at each end by thin metallic ribbons 3 and 4 to form a rectangular frame. Said thermostatic elements are preferably placed back to back so as to oppose each other and each has a hole 5 near its center through which protrudes the reduced and slotted end 6 of adjusting screws 7, 7'. Each of the connecting ribbons also preferably has a central hole or slot 8, the rectangular, frame being anchored to the base casting 10 by a bolt through the slot in the lower ribbon 4. Said screws 7 and '7 are threaded into arms 12 extending from said casting so that by turning one or the other of said screws in and out, the tension or buckling of the adjacent strip may be altered at will.

The upper slot 8 engages the glass stem 13 on the contact element 14. Said element is in the form of a sealed glass tube firmly clamped at its two ends in spring clips 30 and 31 bolted to lugs 32 on the base casting. Through one end of said tube extends electric wires 16, 17 leading to make and break contacts 18 and 19 within the tube. At the outer ends, said wires are connected to threaded terminals 32' for leading in current thereto. The upper contact 19 is shown as mounted on a leaf spring 20 so that the com tacts are biased to a closed position. Rod or stem 13 is sealed adjacent its inner end in a thin walled corrugated glass reversely bent mem- U ber 22, so that the inner end of said rod may be readily moved laterally against the flexibility of member 22 by slight pressure on the outer end thereof. At its inner end said rod bears against contact 19 so that in Fig. 1 said contact may be opened by pressure to the left on the upper end of rod 13 (see arrow), while pressure to the right will permit the contact to close.

The thermostat unit is preferably mounted for lateral adjustment in the lamp box 33 so that ac- T5 curate positioning of the strip 1 may be obtained with respect to the beam from the are. To this end the unit is riveted or otherwise secured to a plate 43, which in turn is provided at its lower end with flanges 44 engaging slotted'trackways 45 in bracket 46 on the housing 33. A stem 47 journaled in housing 33 is threaded through a boss 48 on said plate so that by turning knob 49 on said stem the thermostat unit may be adjusted.

In setting the device, the screw '7 on strip 2 is backed off until thecontact is closed. Then screw 7 on strip 1, on which the arc beam is adapted to fall; is backed off until the contact is completely open. This places the greater tension on strip 2 which is suflicient to hold the contact open by pushing the top of rod 13 to the left in Fig. 1 until the arc beam strikes the strip 1. This causes said strip 1 to buckle inwardly at its ends, thus lessening the tension opposing that of strip 2 and permitting the contact to close under the action of spring 20.

I also preferably locate at the thermostat a means for observing the position and burning conditions of the arc. This may consist of a ground glass window or screen 35 on which the are image falls and which may have graduations 36 thereon. A small window 37 may be provided in an adjustable metal frame 38 having a forked end 39 adjustably clamped by said screw 40. Said window may be positioned so that when the positive tip burns back near the rear thereof, the thermostat should start the feeding mechanism.

My thermostat may be mounted on the lamp in a position similar to that shown in my copending application Serial No. 593,004, filed February 15, 1932 for Automatic projector lamps. Accord-- ing to this prior application, the image of the arc is reflected by a mirror 41 to a point adjacent the thermostat element 1, the arc image being visible through the ground glass window 35. Fig. 5 represents my thermostat as used in connection with a projector lamp, it being understood that it controls the feed of the positive electrode 40' in any suitable manner, such, for example, as outlined in my aforesaid prior application, to maintain the crater at the focus of projector lens 42. Y

It will be obvious to those skilled in the art that my invention, especially the form shown in Figs. 1 to 4, may be adapted, by slight modification, for more general uses than a beam controlled theremostat. For instance, if the compensating strip 2 were replaced by a plain metallic strip, the device could be used as an ordinary thermostat to regulate the temperature of ventilating or refrigerating machines. In this case the screws 7 and '7 should be so adiusted that the contacts 18 and 19 are normally open, but upon a rise in the temperature in the refrigerated space above the desired amount, the inward bending of the outer ends of the strip 1 would permit the contact to close, thus starting up the refrigerating plant. Obviously, also, the device could be used for regulating heating plants. In such case the thermostatic strip 1 should be reversed so that on rise in temperature the ends tend to curl outwardly instead of inwardly. In such case the rise in temperature of the room would pull' the top of the glass rod 13 to the left in Fig. 1 thus opening the contacts and shutting off the heating plant.

Strip 2 in this case should either be a plain metallic strip with the screw 7' adjusted to give no tension therein, or it could be eliminated entirely.

In accordance with the provisions or the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a thermostat, a vacuum tube, a pair of contacts enclosed therein, two opposed thermostatic elements, and flexible means connecting the same, said elements being under tension as to exert pressure against the contacts proportional to a difference of temperature of the elements.

2. In a thermostat, a vacuum tube, a plurality of contacts enclosed therein, and means for operating the contacts from a point without the tube including a plurality of thermostatic elements located on either side of the tube so mounted as to be under tension relative to each other and so positioned that an increase of temperature of one element will release tension on another element and cause the contacts to close.

A differential thermostat having two heat sensitive strips, flexible means connecting said strips at each end, each strip being under tension at its middle so that the pull of one strip opposes that of the other, and means for adjusting said relative tension.

A thermostat controller comprising a sealed evacuated glass tube, spring pressed contacts therein, a rod sealed in said tube and extending without the same, a thermostatic strip, a common support for said tube and strip for mounting said strip and tube side by side, and means connect-- ing said strip at one end to said rod to vary the pressure exerted by said strip on the end oi the rod as the strip bows under temperature changes.

5. A thermostat controller comprising a sealed evacuated glass tube, spring pressed contacts therein, a rod sealed in said tube and extending without the same, a thermostatic strip, a common support for said tube and strip for mounting said strip and tube side by side, means connecting said strip at one end to said rod to vary the pressure exerted by said strip on the end of the rod as the strip bows under temperature changes, and means for adjusting the bow or tension of said strip.

6. A thermostatic controller comprising a M sealed evacuated glass tube, spring pressed con tacts therein, a rod sealed in said tube and can tending without the same, a pair of spring strips, at least one of which is thermostatic, a common support for said tube and strips for mounting said 101] strips on opposite sides of said tube, and flexible means connecting said strips at each end, said means at one end also being connected to said rod.

I. A thermostat controller comprising a sealed 105 evacuated glass tube, spring pressed contacts therein, a rod sealed in said tube and extending without the same, a pair of spring strips, at least one of which is thermostatic, a common support for said tube and strips for mounting said lid strips on opposite sides of said tube, flexible means connecting said strips at each end, said means at one end also being connected to said rod, and adjustable means in said support intermediate the ends or each strip ior varying the relative bow or tension thereof.

8. A thermostat controller for projector lamps comprising a sealed evacuated glass tube, spring presed contacts therein, a rod sealed in said tube and extending without the same, a pair of opposed thermostatic strips, 8. common support for said tube and strips for mounting said strips on opposite sides of said tube, and flexible means connecting said strips at each end, said means at one end also being connected to said rod.

9. A thermostat controller for projector lamps comprising a sealed evacuated glass tube, spring pressed contacts therein, a rod sealed in said tube and extending without the same, a pair of opposed thermostatic strips, 9. common support for said tube and strips for mounting said strips on opposite sides of said tube, flexible means connecting said strips at each end, said means at one end also being connected to said rod, and adjustable means in said support intermediate the ends of each strip for varying the relative bow or tension thereof.

10. A differential thermostat having two heat sensitive strips, flexible means connecting said strips at each end, each strip being under tension at its middle so that the pull of one strip opposes that of the other, and contact means operable by the movements of one of said flexible means under the differential pull oi said strips.

11. A differential thermostat having two heat sensitive strips, flexible means connecting said strips at each end, each strip being under tension at its middle so that the pull of one strip opposes that of the other, means for adjusting said relative tension, and biased contact means operable means adjacent said strip, and a rod extending by the diflerential tension of said strips.

12. A diflerential thermostat having two heat sensitive strips, flexible means connecting said strips at each end. each strip being under tension at its middle so that the pull of one strip opposes thst o! the other, vacuum sealed contact within and without said vacuum sealed contact means and connected at its outer end to said flexible means whereby said contact means is operated by the differential pull of said strips.

iii: 

